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Definitions T

Tack Weld: A small, temporary weld placed at intervals along a joint to hold it in alignment.

Tandem Axle: Two, independently suspended axles working together on a truck or trailer.

Tearing Dimples: Dimples formed in tearing overload type failures. The dimple and dimple tail have an orientation, which indicates the direction of tearing for application.

Tempering: A process whereby very brittle steel is heated after being quenched. This subsequent heating allows relief of internal stress and for the martensite to transform or change to a more stable structure.

Tensile Dimples: Dimples formed in metals, which deform appreciable amounts under the influence of tensile or pulling stress. Tensile dimples appear on a fracture surface as small cups and called equiaxed.

Tensile Load: A force that attempts to pull apart or stretch an object. A tensile load is applied to a standard test specimen to measure and determine the yield and tensile strength of the metal.

Tensile Strength: Often referred to as the ultimate or highest strength of the metal. Tensile strength is the material's ability to resist forces that attempt to pull apart or stretch it. If the load surpasses the ultimate or tensile strength, the test sample or the item will fracture and separate.

Tensile Stress: A tensile or pulling load applied perpendicular to a particular plain results in a tensile stress. The magnitude of the tensile or pulling stress is the magnitude of the load divided by the area on which that load acts or is applied.

Tensile Test: Also known and tension test is the most widely used and most fundamental type of mechanical test that can be performed on material. This standard test determines the ultimate or tensile strength of a metal. In numerous test procedures, the metals yield strength, elongation and reduction of area ductility can be determined.

Tension: Tension is a pulling stress. Anything pulled, hung, supported, or swung from a material can be subject to the force of tension. Like all forces, tension can accelerate objects or cause them to deform.

Toe Cracking: Cracking in the toe of a weld location where the weld metal joins to the base metal where the metal is to be joined by welding.

Tong: A large oil field tool, basically an oversized wrench, used to hold one side of drill pipe or casing when an additional joint is added to the drill pipe or casing string. Tongs are also used to breakout or take apart a joint of pipe from a string of pipe as the string is removed from the well. A single makeup tong is used to keep the drill pipe or casing string from rotating when the drill pipe or casing string is being added going into the hole.

Tong Mark: Marks produced by the teeth on an oil field tong tool, which bites into the drill pipe, or casing as another joint is added or removed from a drilling or casing string.

Torch: A handheld mechanism through which gases combine to produce an extremely high temperature flame used for welding, cutting or brazing.

Torque (ft. lb.): A measure of how much a force will cause an object to twist, rotate or tighten. The formula is Τ = r x F = r F sin(θ). The units of torque are a force (pounds) times distance (foot), i.e., 10 pounds applied to a lever with a length of 18 inches (1 1/2 feet) is 15 ft.- lbs. (10 lbs. x 1 1/2 feet – 15 ft.-lbs., expressed as 15 foot pounds).

Types of torque:

1) Breakout or Breakaway Torque

2) Makeup Torque

Transgranular Cleavage: A failure mode that occurs at well-defined crystal planes. Cleavage occurs when the metal experiences a high stress being applied to the metal at a high rate of speed and/or at low temperature. Transgranular cleavage fracture denotes an inability to absorb impact energy. The visual characteristics of cleavage are cleavage steps, tilt boundaries, feather and herringbone markings, etc.

Transgranular Fracture: Can be a brittle or ductile fracture that follows the pattern of grains in the individual lattices of the material. It is a fracture path that proceeds through metal grains rather than around the edge of metal grains. If transgranular fracture is brittle, a fracture pattern called cleavage will be displayed; if it is ductile, transgranular fracture produces ductile dimple fracture topography.

Tubercles: Corrosion products resulting from localized corrosion. These knoblike mounds are scattered over the corroding surface. They can grow into tubes or plates, which can, in time, occlude the entire pipe interior.

Undercut: Undercutting is a welding flaw that appears as a groove in the parent metal directly along the edges of the weld. This type of flaw is most commonly caused by improper welding parameters, particularly the travel speed and arc voltage.

Uniform Corrosion: Corrosion, which uniformly and more or less evenly corrodes a metal surface without concentrated pitting corrosion in a localized area.

Valve: A mechanical device which when opened will allow flow of liquid or gas.

Volcanoing: Plastic permanent deformation of metal around a bolthole. The deformation, in the form of a volcano, results from pushing the steel around the bolthole over a hexagonal nut or bolt head.

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J.E.I. Metallurgical, Inc.

5514 Harbor Town
Dallas, Texas 75287

Phone: (972) 934-0493
Fax: (469) 737-3938
Email: r.c.jerner@metallurgist.com

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